Discharge tube



G. CLAUDE DISCHARGE TUBE Sept. 13, 1932.

Filed March 51 I NVENTOR' 10 BY HIS ATTORNEYS Patented Sept. 13, 1932 UNITED STATES PATENT orrlca GEORGES CLAUDE, O1 BOULOGNE SUB SEINE, FRANCE, ASSIGNOB T CLAUDE NEON LIGHTS, INC OF NEW YORK, N. Y; A CORPORATION OF NEW YORK mscnmr: roan Application flled' larch 31, 1931, Serial 1T0. 526,608, and in France April 2, 1930.

5 xenon, emit light under the mfluence of an electric discharge which appears to the eye to be monochromatic. Neon, for exam e, emits a characteristic orange red light.

spectra of such gases is discontinuous and contain certain lines characteristic of the particular gas in question. The spectrum of each gas has, moreover, certain lines or groups of lines which predominate and to which is due the color by which the eye characterizes the light from such gases. None of the individual rare gases is therefore well suited for general illumination purposes as such, because a light satisfactory for general illumination purposes should have a rich and well proportioned spectrum having a com osition as close to thatof daylight as possib e, and being made up of wavelengths from all the moreim ortant portions of the visible specttempts have been made to supple ment the spectral deficiencies of the individtrum.

ual rare gases by mixing with a rare gas, as for example neon which is rich in wavelengths in the red and yellow portions of the spectrum, a substance capable ofemitting so light which is rich in wavelengths in the green, blue and violet portions of the spectrum, as for example mercury. Such attempts, however, have failed to produce the desired result because the light emitted by such a mixture'is almost entirely that of the heavy metallic vapor. Under suchrcircumstances the emission of light due to the recombination of ionized atoms appears to be restricted to the heavy metallic vapor to the 4 exclusion of the rare gas. Various theories have been advanced to account for this phenomenon but whatever may be the correct theor it is afact that the attempts which have een described to obtain a substitute for natural daylight or a light having a rich and well proportioned spectrum by merely mixing the vapors of a rare gas, more particularly neon, with a heavy metallic va or, such as that-of mercury, have not succee ed.

The present invention, however, provides a new and improved method and apparatus and, according to the teaching of the present invention, it is possible to pass an electric discharge through a tube' containing a rare gas and a heavy vapor in such amanner that not only is light emitted from the heavy vapor by ionization and recombination of the'atoms, but light is also emitted by the rare gas and the respective lights are blended, with the result that the spectrum of the re- 'sulting light is well proportioned and contains wavelengths representative of the more important portions of the spectrum. This is accomplished broadly by taking advantage of the widely diflerent physical properties of a rare gas on the one hand, as for example neon, and a heavy metallic vapor on the other" hand, as for example, mercury. Neon is a typical fixed gas and remains as such throughout an extremely wide temperature range. Its boiling point in fact is 239 degrees below zero centigrade. Mercury, on the other hand, at ordinary room temperature is a liquid with aboiling point of approximately 357 degrees above zero centigrade, and a low vapor pressure at ordinary temperatures.

Mercury, therefore, can be very readily condensed or changed from the vapor to the liquid state,- whereas the rare gases are condensed only with very great relative difiiculty.

According to the present invention, while the various parts of the tube are in communication with each other, the region or regions intended to containthe mercury are so. arranged that they can be readily cooled to prevent the movement or diffusion of the mercury vapor beyond that region or regions. Consequently, the remaining portions of the tube contain, for the most part, neon or other suitable rare gas as free as possible from contamination with mercury, and in these portions the electrical discharge causes the emission of light characteristic of the particularrare gas used such as neon.

' The invention, however, comprises the utilization of another principle, and that is that when neon and mercury vapor are mixed together the neon light will be distinctly visible if the current density is sufliciently high notwithstanding the presence of the mercury vapor. Therefore, in the method and apparatus of the present invention, those regions from which it is intended to exclude the mercury vapor, as above described, may, in fact, be contaminated by a small amount of such mercury vapor, but the current density of such ortions may be rendered high enough to 0 set this possible contamination and to render it certain that the rare gas in those portions will be excited, as by ionization and recombination of the atoms, so that the said rare gas will emit light predominating over or to the excluson of the heavy vapor.

Moreover, not only does the invention teach a method and apparatus for obtaining a segregation of the vapors of an easily condensable vapor and a rare gas within the same common tube and a method for controlling the current density in the portions containing the rare gas, but it also includes means for blending the light'emitted by the rare gas and vapor, respectively, in the same common tube, so as to obtain a blended light having a rich and well proportioned spectrum which may be used as a substitute for daylight inasmuch as it is composed of wavelengths from all the .essential portions of the spectrum.

The teachings and principles hereinabove broadly describedmay be exemplified by reference to a specific example and structure,

although it will be apparent that this specific illustration is employed merely to show .one specific device and method for applying the broader teachings of the invention.

Reference should, therefore, be made to the accompanying drawing which forms a part of the disclosure and in which the figure is a section through a tube constructed in accordance with the invention.

A discharge tube or vessel 1 has a metallic cathode comprising a metal which vaporizes at the temperatures produced by the operation of the tube, as for example the mercury cathode 2 preferably positioned at the bottom of the tube. The tube 1 carries a press 3 through whicha lead-in wire 4 passes into the tube and is immersed in the mercury pool 2 for electrical connection therewith.

A small size tube 5 is positioned axially within the larger size tube 1 and has its lower end enlarged to'form an electrode chamber 6. The small sized tube is secured within the. tube by sealing the end 8 of the electrode chamber 6 to a press 7 carried by the larger tube 11;. The small tube may also be supported within'the large tube by a supporting member 12 whichhas passages therethrough so that the tube is connected throughout its length. An electrode 9 is carriedwithin the small size tube in the electrode chamber 6 andis electrically connected to the lead-in wire 10 passing through the press 7. The end 11 of the small size tube 5 distant from each tube is connected with or open to the other tube through the open end 11 of the small diameter tube 5. The open end 11 of the small tube preferably extends into a bulb ous end 13 upon the upper end or end opposite from the end which contains the mercury pool electrode 2. The open end 11 of the small tube 5 may be restricted such as 'by reducing or narrowing the size of the tube at the end. The tube is filled with a gas such as neon or other rare gas.

In operation, the electrodes 2 and 9 are connected to a source of electrical potential and the discharge passes from the anode 9 to the cathode 2 through the axial or small tube 5, through the open end 11 of the tube into the larger tube 1 and down this tube to the cathode. The mercury in the mercury pool cathode vaporizes under the heat of the discharge or passage of current, through the tube, which vapor fills the larger tube 1 and the luminosity radiated has the characteristic color of the cathode metal or mercury.

The large diameter tube provides a large cooling surfaceand the mercury vapor condenses thereupon throughout the length of the tube participation in the discharge at this point.

The condensed mercury flows back to the cathode pool upon the walls of the tube.

With mercury vapor lacking within the axial or inner small tube 5', the rare gas therein will radiate a light having the characteristic color of the gas which, in the case of neon is the well known orange red color of a neon discharge. The heomwill continue to emit its characteristic color even though some mercury vapor does manage to pass into the inner tube because-of the relatively high current density in the inner tube 5. It is to be noted that the inner tube is brought to a higher temperature than the remainder of the device because it is heated inside and outside by the discharge. X,

The device described herein'gives particularly good results with neon and ercury, because with this mixture the neon emits light predominating over that of the .rriercury where the current density is relatively high,

.as. in the tube 5. Conversely, where' the curso that in the smaller tube the current density, that is the current per unit cross sectional area, is considerably greater than the current in larger proportion than if a mixture of neon and mercury had been used in the usual discharge tube.

This device may also be described then as. a luminous discharge tube havmg a mixture of neon and mercury in which a'discharge having a high current density is superimposed or surrounded by a discharge having a low current density.

The preferable easily condensable vapor described herein is mercury, but it is possible to employ other easily condensable substances. Cadmium, potassium and other suitable metals may be employed although they are not the equivalents of mercury, and among organic substances ,anthraquinone may be utilized. I 7

By a proper selection of rare, gases and vapors so that the wavelengths of the vapor and those of the rare gas are mutually complementary a superimposition of the radiations of the gas upon those of the vapor produces a light havin a rich and well proportioned spectrum adapted for use as a substitute for daylight.

It will be noted that the invention comprises, therefore, a method of superimposing on the radiation of an easily condensable vapor the radiation of a rare gas, as for example neon, the gas'and vapor being enclosed in a common vessel,.which comprises cooling a particular region of the vessel to prevent the movement of the vapor beyond that region whereby the vapor and gas are segregated into respective regions, and passing an electrical discharge through those respective regions.

It will also be noted that the invention comprises a luminescent tube containing electrodes, and having regions containing, respectively, a rare gas and an easily condensable vapor, and means to cool the vapor containing region to prevent access ofsaid vapor to the region containinglthe rare gas as well as means to pass throug the region containing the rare gas a discharge current having a density higher than that to be passed through the region containing the vapor.

The principle referred to herein relating to the control of the current density in a characteristic neon color is made to, predominate over'that of the mercury, will be found to be more fully described by reference to my co-pending application Serial No. 80,707

file'd'in the United States'Patent Oflice J anuary 12, 1926 and in France January 22, 1925. What is'claimedis:

1. A luminous tube comprising a small diameter tube having an open end, an outer tube; surrounding the small tubeand connected therewith through the open -end of the small tube, the outer tube having a large cooling surface in contact with the surrounding atmosphere, a mercury pool-electrode at the end of the larger tube which isidis'tant from the connecting ends of the tubes, a gas throughout both tubes, and an electrode at the closed end of the small tube.

2. A luminous tube comprising a small di ameter tube having an open end, a larger tube surrounding the small tube and connected therewith through the open end of the small tube, the larger tube having a large cooling surface in contact with the surrounding atmosphere, the endof the larger tube having 1 a reatly increased cooling surface into which end the open end of the small tube pro ects, the two tubes being connected through the open end of the small tube, a

mercury pool electrode at theend of the larger tube which is distant-fromthe'connecting ends of the tubes, a gas throughout both tubes, and an electrode at the closed end of the small tube. v

In testimony whereof I aflix m si ature.

' .GEoizGEs c A E.

- mixture of neon and mercury, whereby the 

